It is known how to drive auxiliary devices such as e.g. electric generators from a rail car axle by means of a belt running over a driving pulley keyed on the car axle and over a smaller driven pulley keyed on the shaft of the electric generator. However, when having to drive a hydraulic pump which is intended for energizing hydraulic servo-drives such as those for actuating doors, this kind of transmission is complicated and expensive, and it cannot be supplied to an user under a form which could readily be assembled by the user. It is also possible to provide a driving system using bevel gears on the end of the axle, for driving a transmission shaft having universal joints, this shaft being further connected to the pump shaft; however, this kind of transmission is also costly and comprises too many mechanical parts, each one of which is subject to breakdowns.
On another hand, the regulatory authorities of railways prescribe that axles must not be subjected to any axial stress which could be liable to cause a shift, however small, of the axle along its axis.
In an attempt to solve this problem, French Pat. No. 86.00480 describes a rail car axle provided on at least one of its ends with a hydraulic pump, characterized in that the hydraulic pump is a slanted-plate pump having its axis coaxial to the said axle; said slanted plate driving a plurality of pistons parallel to the axis of the car axle and located within a pump body provided with a cylindrical skirt inside which is placed the slanted plate, said skirt carrying the bearings which support the slanted plate and its shaft, and comprising the means for fastening the pump on the hub cap of the axle.
According to this prior patent, the linkage between said axle and the pump drive shaft is achieved by means of a connecting member formed of a plate and a shaft, said plate being biased by a spring so that it will rest against the end of the axle, while said shaft is rotatably linked with the pump shaft while remaining free to slide axially relatively thereto.
Again according to this prior patent, the pump skirt is fastened either directly onto the hub cap of the axle, by screwing it inside the central hole of the hub cap as it extends through said hole, or else by means of a support member fastened to the hub cap, externally thereto.
However, the fact is to be taken into account that in several countries, including the U.S.A., rail car axles are not provided with hub caps, so that the pump fastening system described in the above-mentioned French Pat. No. 86.00480 is not applicable.
In the U.S.A., the linkage between the roller bearing housing located on the end of an axle and the undercarriage frame is effected by means of an adaptor piece.